Lens.



1G. A. 11. KELLNER. .LBNS; ,APPLI'OATIOR FILED OCT. 10, 1910.

Patented Mar. 26, 1912;

. vehicles Si UNITED striurns PATENT ()FFICE. I

GUSTAV A. H. KELLNER; or ROCHESTER; NEW roan, Assmuonfaro BAUSGH & LOMIB OPTICAL COMPANY, oraocHnsirEaaNEw-Yomt a CORPORATION or NEW YORK.

LENS.

Specification of'Letters Patent.

Patented Mal-. 26, 1912.

Applieation filedoctober 10, 1910. Serial N 0. 586,139.

To all wkom'it may concern: 7 I

Be it known that I, Gus'rav A. H. KELL- Vented certain new and use'tullmprovemcnts in Lenses, of which the following is a. lull,

clear, and precise specification;

My invention relates to lenses, particularly to those of the Fresnel type and contemplatesimproved construction which will adapt such" ISBS for more efiicient use on as automobiles, railway cars or the like. Lenses of this type comprise a plurality oi retracting zones or annuli; In headlightsorlalnps it desirable to be able to observe at any time the cond-itionof the light source; particularly wherc the source is in the form of an oil lamp. It is impossible to obtain a clear-cut image of the flame through the retracting zones and several constructions have been resorted to inthe prior art to PTOVlLlGD'lQRIlS whereby the flame could be observed through some part of the lens without opening the lamp. In some of these prior constructions a lens is continuedbeyond the retracting zones to form a. plain annularhand at the outer edge of thelens througl'iwhich the flame can be observed. This constructimi, of course, greatly increases the renders a gi' atpe1.' cent. thereof useless for the lighting purposes for which the lens'is to be used, this outer annular band in some.

cases constitiiiting one half of the lens surface. FUIl'llOlllH'il'P, with this construction the tlainc canbe viewed only from an angle.

Also in prior lenses of this class no attempt the retracting zones, which base surfaces in most cases are parallel with the principal axis of the lens o are only slightly at an angle therewith suilieient t-o'enable-the lens to be Withdrawn from the mold after cast ing thereof. 1 Inlatlt, inallthese prior lenses the aim has been to retain only such rays as are parallclcr ap 'irommately parallel to the principal axis andsthe base faces of the retractingzones have purposely been constructed *at a small angle so that incidentrays would upon retraction falllwithm the izc of the lens'and' to arrange this sight section at suchpart of the lens where a true elevation View can be obtained of the flame .or other source; to eliminate the prior art outer sight band of wasteful area and to concentrate the sight section'atthecenter of the lens into a very small area ascompared with the-entire lens area; to so arrange the optical dimensions of the sightsection that a clear elevation image of the flame can he obtained without blinding'the eyes while at the same time prevent- ;:iug tlie loss )f' any appreciable number of useful llghtwrays emanating through the sight sectiong to utilize fully the base faces of the ref action zones for attaining diver gent emanating rays at proper angles to illuminute the ground-directlyin front of and at the sides of the path of travel of the ve* hicle; and to do this without in any way inr pairing the full etficienoy of the axial par..

allel' raysrelracted from theinner faces of the refraction zones; and in general to provide improved construct-ion which will Inatcrially reduce the size and weight of the lens, yet which willcause the efficiency of the lensto be greatly increased.

Lenses which incorporate the above features of my invcntioli are clearly" described in the following specification and shown on the accompanying drawing; in which drawing' 7 Figure 1 is an interior planview of a lens with the left half thereof broken away, Fig. 2 is av sectional View taken on plane 22, Fig.1, and Fig. 3 is similar sectional View but showing a son'iewhat modified arrangement, has been made 'to utilize the base surfaces of The lens has an outer spherical convex surface 1, and aninner central concave surface Q the refractingzones or annuli 3 extending from the convex surface 2 tothe extreme circumference of the lens.

. I In Figs. 1 and 2 four retracting zones 3 3", 32 8, are shownhaving the iniieifci'invex surfaces 4. l 4, 4, respectively. The

.100 radii of these varioussurfaces are so 1310" of the.

allel to the principal axis A. As shown in Fig. 2, the incident rays 71 emanating from ,the focal center and striking the convex refracting surfaces are refracted and emerge as the illuminating rays r which are substantially parallel with the principal axis A. The section of the lens bounded by the inner concave surface 2 and the outer convex surface 1 forms a sight section .9 through which rays emanating from the principal focus are slightly refracted outwardly. As shown, the incident rays .71 passing .through this sight section emerge as rays r which deflect slightly from the principal axis. The image of the flame observed through this sight section will be slightly reduced in size but the image will be distinct and clear-cut and can be observed without blinding or undue straining of the eyes. Furthermore, a true elevation view of the flame can be obtained and thus the flame can be adjusted with great precision without opening of the lamp casing. This inner sight section need only be large enough to enable a view of the entire flame, and its area as compared with the entire lens area is very small indeed. In

the lens shown in Fig. 2, the sight area involves only about one-thirteenth of the entire lens surface, whereas'in prior lenses the sight area which extends about the outer edge ofthe lens involves about one-half of the total lens area. Although the emerging rays. at the sight section slightly diverge, this is no disadvantage, as the diameter ofthe sight section is small and the parallel rays 1' from the refraction zone are of sufficient number and intensity to give suflieient forward illumination, while the slightly diverging rays r through the sight section are more efficiently utilized in illuminating the roadway a short distance ahead of the vehicle and to the sides. In other words, the slight loss of a small core of parallel rays is more than offset by the great advantages obtained by the central sight section which enables vision of a clear-cut elevation view of the flame and which results in decrease in weight and size of the lens.

In prior lenses the base surfaces 5 of the refraction zones are parallel with the principal axis or are given only sufficient angularity with'respect to the principal axis to enable the lens to be better drawn from the mold after casting thereof. In such construction, however, incident rays from the focus would be refracted within the critical angles or would emerge at angles which would render them useless for illuminating purposes. In accordance with my invention these base surfaces are given sufficient angularity with respect to the principalaxis so that illuminating rays emerge at a useful angle to give diagonal illumination in all directions, which is very desirable on vehicles such as automobiles. As shown,

the incident rays f entering the refracting zones at their bases are refracted into diagonal rays 9 which are parallel or approximately so. In the construction of lens shown the base surfaces are parallel and have angles of ten degrees with the principal axis so that the emergent illuminating rays 9 are inclined from about fifty-five to sixty degrees with respect to the principal axis. Depending, of course, upon the angle of the base surfaces the resultant emerging rays can be given any angular divergence from the principal axis. Thus in my improved lens not only are all the useful forward parallel rays retained but in addition another useful field of diverging rays is obtained and utilized to the fullest advantage by merely sufliciently increasing the angularity of the refraction zone bases.

. We have, in fact, three very useful illuminating fields, namely, a field comprising the substantially parallel rays r which illuminate at a distance ahead of the vehicle,

a field comprislng the rays 7"" emerging through the sight section and illuminating forwardly and outwardly at a shorter distance from the vehicle, and a field comprising the divergent or diagonal rays 9 which illuminate forwardly and outwardly close to the vehicle. Thus in my construction as compared with that of the prior art a much greater amount of light is obtainable, a better arrangement of the illuminating rays is possible, and at the same time this is all accomplished by a much smaller and lighter lens and one in which much' better observation can be made of the illuminant.

In Fig. 3 is shown a somewhat modified arrangement in that five zones 3*, 3", 3, 3,

' 3, are provided, thus giving a greater lens aperture. In Fig. 2 the base surfaces of the refraction zones are straight, but in Fig.

3 these surfaces are curved and the curvature could be either convex or concave. As shown in Fig. 3, these base surfaces have spherical convex curvature and the radii of curvature of the various bases may be the same or diflerent. As shown in Fig. 3, the radii of these surfaces are different and the emergent rays 71. diverge relatively, as

shown, and give a wider diagonal field of illumination. The radii of curvature of the inner surfaces 4 4,, 4, 4, 4 of the retracting zones are such thatthe emergent rays 7' are substantially parallel with the principal axis A and the ray direction of.

the sight section 8 is the same as that shown in Fig. 2. The outer edge 12 of the lenses forms an annular tongue which is adapted to be received in a suitable annular pocket of the lamp frame towhieh the lens is applied.

'lhe base surfaces of the refracting zones can, therefore, be straight or can be given any form of curvature and a pitch wlth reference to the principal axis which will cause incident rays to be refracted into useful illuminatin rays. The lenses are of practically uniform thickness throughout, the distances between the inner ends of the bases 5 and the outer surface 1 being equal and the axial thickness of the sight section a being also equal to these distances. The lens Will, therefore, be free from detrimental strains during the formation and cooling thereof.

Modifications can, of course, be made in the construction, which will still come within the scope of my invention, and I do not, therefore, limit myself to the particular construction shown and described, but

I claim the following:

A circular headlight lens having an incident concave surface of one curvature with a small central section of greater curvature, refracting' prismatic extensions on the sur" ce between the central section and the periphery of the lens, and a common emerface to refract incident rays into emergent rays substantially parallel with the axis to illuminate at a distance from the lens, the base surfaces of the extensions cooperating with the emergent surface to refract incident rays into divergent rays for illuminating at a short distance in front of the lens, and the central convex concave section refracting incident rays into rays of small divergence for illuminating at an intermediate distance in front of the lens, said lens being of substantially uniform thickness. GUSTAV A. H. KELLNER. Witnesses:

G. WILLARD RICH, RUSSELL B. GRIFFITH. 

